Apparatus for coating thin stiff sheets



Feb. 13, 1951 c. J. cRoss ET AL 2,541502 APPARATUS FOR coATING THINsTIFF sHEETs Filed June 14, 1948 3 Sheets-Sheet 2 I N VEN TORS CARL J.CROSS Y SHERMAN W. LYNCH ATTORNEYS Feb. 13, 1951 C J CROSS ET AL2,541,502

APPARATUS FOR COATNG THIN STIFF SHEETS Filed June 14, 1948 3Sheets-Sheet 3 Na ;f

1 N VEN TORS CARL J. CROSS SHERMAN W. LYNCH ATTORNEYS Patented Feb. 13,1951 UNITED STATES PATENT QFFlCE APPARATUS FOR COATING THIN S'lJlFFSHEETS v Carl .I. Cross, Runnemede, N. .I., and Sherman ration of `New Jerey Application June 14, 1948, Serial. Nov. 32,874

(i Claims.V (Cl. 91- 1 8) This invention relates .to systems for coatingthin .stiff sheets of any .densematerial and lparticularly relates tothe coating of lthin metal laminations.

In the manufacture of laminations for the cores of electromagneticdevices, such as transformers, filter coils, .and the like, used incommunication or power circuits, it is usual, after completion ofmachining Operations, to anneal the laminations for attainm'ent orrestoration of desired magnetic properties. It is a purpose of theinvention to reduce the time and cost of coating the individual gorelaminations with material which prevents them from ,sticking togetherwhen stacked and subjected to annealing temperature.

In accordance vwith the inventio'n, the .laminations While retained instacked formation by force applied lengthwie of the stack are subjectedto vibration longitudinally of the Stack so that the individuallaminations due to their inertia rapidly and repeatedly separateslightly sc as to permit coating material to flow between them intocontact With their adjacent faces. More specifically, the laminationsare stacked in a work-holder having a slidable member biased as by aweight against an end of the Stack and the holder is attached to avibratory frame,v or equivalent, whose amplitude and frequency ofVibration are preferably Yariable to adapt the apparatus to the inertiacharacteristicsof different stacks and/or to the flow characteristics ofdifferent coating materials.

Though primarily devised vfor vcoating magnetic core llaminations Withinert powdered materia] for prevention of their sticking together duringannealing, the apparatus is suitable for application of other coatingmaterials to laminations having other purposes.

The invention further resides in systems having features herenafterdescribed and claimed.

For a more detailed understanding of the invention, reference is made tothe accompanying drawings in which:

Fig. 1 is a perspective view of a work-holder for a stack oflaminations;

Figs. 1a, 1b and lc illustrate the relation of structure of Fig. 1 tolaminations of different shape;

Fig. 2 is a schematic perspective view of an apparatus suited to performthe preferred method of coating;

Figs. 3a and 3b are explanatory figures referred to in discussion ofmovement of the individual llaminations of the stack of Figs. 2 and 4 to6;

Eigs. l, 5 and ,6 are eiplanatory figures illustrating lengtheningdofthe'staclf` during Vthe Coatingoperatnj' i Fig. '7 is vpartial plan viewof a modificatior' of'Fig. 2;

Fig. 8 is a sectional view of an annealing .tray containingapluralityofstacks of laminations;v

Fig. 9 is a1 perspecti've view, partly broken'away, of anannealing boxcontaining a plurality of the traysof Fig. ;8;`

F'ig.` 10` is a perspetive view, referred to in discussion of recoveryof Vthe coating material; and Fig. 11 is a lperspective view showingCleaning of anannealedl Stack.

vAs Abriefiy mentiond above, before disprosition of'a `Stack oflaminations in an annealing furnace, they are c'oated or covered withinert material which aifords access o f a de-oxidizing or inert gas tothe surface of the laminations and also maintans the laminati'ons out ofphysical contactV with each other. Heretofore the step of coatingthelaminations has been a slow, manually-performed operation whichparticularly in the 'case of the smaller laminatiOnS, such as are usedinr the small transformers and inductors lifid inwidget.radiQSLhearing-aids and the like, represented an unduly large and,variable' factor in Vthe costof the laminations. By recourse toapparatus herein decribed, the expense incurred inV this preliminarystep of the annealing operation Ais :very materiallyreduced and can bequ1te accurately predicted for successive runs of similar lamin'atons.

` Referring to Fig. 1, the holder IB preferably comprises abottonrwall II, a side wall |2 and an end'wall |73, a1 l preferably permanentlysecured to one another to form a trough or receptacle in which a stack14 of laminations may be disposed. O ne endy o fthe sta'ck Aengages thefixed Wall |3 of the holder iii and the other end of the stack isengagedby aV slidable member or end wall lEi whichy is pressed orheldagainst it so to retain the .individual laminans in place- IT,orequivalent, overlie the stael to prevent the laminations from beingdislodged in handling of i thev holder by an operator or during thevarious Operations beqyetlv deribed- .In the preferred constructionshown, the red or bars I'i' are attached to the slidable member 6 andfreely pass through and beyond the end wall 13.

' When the laminations are L- shaped, as are lamnations I of 1"' igs`.'1 and 1a, one leg of the laminations is disposed adjacent the side wall|2 of .th'hlder and'the Other leg ,of vthe laminations rests upon vthe.bttem Tima as apparent The bars 3 from Figs. 1 and 1a, the rods i'i, orequivalent, cooperate with the bottom and side walls of the holder' toretain the laminations in place.

When the laminations are U-shaped, as are laminations B of Fig. 1b, therods I'l are disposed between the two Vertical legs of the laminationsand cooperate with the bottom of the holder ll to retain the laminationsin place. With U-shaped laminations, it is not necessary that the holderhave a side wall |2 but to enable the same holder to be used for variousshapes of laminations, the construction shown is preferred.

When the laminations are E-shaped, Fig. lc, the rods l'i arerespectively disposed between the central Vertical leg' and the twooutside legs and so cooperate with the bottom wall H of holder l toretain the laminations I5C in place. Again, for this shape of laminationit is not necessary for the holder to have a side wall 12.

The holder IO is preferably of the open construction shown to facilitateloading and unloading and to aiford ready escape of excess coatingmaterial but it shall be understood the holder may have a second sidewall and/or a second fixed end wall.

For laminations of widely differing size, it may be necessary to usework holders of correspondingly different dimensions but with the typeconstruction shown, only a small number of Work-holders is necessary toaccommodate a substantial range of sizes and shapes.

After a stack of laminations has been disposed in a holder Ill, theholder is secured to a vibratory frame 18 which, as shown in Fig. 2, mayhave a jaw l9 operable by a clamping screw 29 rigidly to attach a holder|0 to the frame ll. It shall be understood that the holder IS may be anintegral part of the frame IB, but it is desirable to have thework-holder detachable from the frame II. Among other advantages, thispermits the loading of one holder with laminations while another holderis being vibrated for coating of the laminations therein; it alsopermits the same vibratory frame 18 to be used with different holdersrespectively suited for laminations of widely different sizes andshapes.

After the holder Ill is attached to the vibratory frame |8, theprojecting ends of the rods |'l are attached, as by cord 25, to acounterweight 26, or equivalent, which Supplies a biasing force tendingto compress the stack |4 between the fixed end-wall |3 of the holder andthe slidable end-wall 16, or equivalent. The pulley 21, or equivalent,is provided so that the downwardly acting force of counterweight 26 maybe converted to a force acting lengthwise of the stack. For reasonswhich will hereinafter appear, it is desirable to use a weight insteadof a spring to insure, throughout the coating operation, substantialconstancy of the biasing force applied to the Stack. It shall beunderstood, however, that biasing force may be and preferably isdifferent for stacks of differently dimensioned laminations and,accordingly, the counterweight 28 is composed of individual weightswhich may be added or removed to accommodate the different inertiacharacteristics of the different stacks.

In the particular arrangement shown in Fig. 2, the vibratory frame |8 ismounted upon a pair of rods 28 which are slidable in the stationaryframe members 29 of the machine. The frame |8 is biased as by springs 30for movement in one direction. The cross member 3| connected to the rods2B or to any other part of the vibratory frame assembly is engaged by acam or eccentric 32 driven by electric motor 33 or any other suitabledriving means. The amplitude of vibration of frame IB may be regulatedin any desired manner; in the particular arrangement shown by way ofexample, the stop 34 is adjusted by hand-wheel 35 to limit the extent towhich the frame |8 may be moved in one direction by the biasing spring30 and the extent to which the frame |8 may be moved in the otherdirection by the cam 32, or equivalent, is or may be varied by shiftingthe position of the motor support 36 which threadably engages a screw 31rotatable by the hand-wheel 38. In any event, whether by the particularmeans shown or by other equivalent means, it is desirable to provide fora variable amplitude of vibration of the frame IB to obtain Optimumresults with stacks of different sizes, weight and othercharacteristics.

It is also desirable that the frequency of vibration of frame 18 becontrollable to suit the apparatus to different stack loads. In theparticular arrangement shown in Fig. 2, this is conveniently effected byprovision of a rheostat 39 in Circuit with the motor 33. It shall, ofcourse, be understood that other regulating means suited for theparticular chosen type of motor may be used and that the rheostat 39 isgenerically illustrative of any speed control means for varying thefrequency of vibration of frame |8.

A coating material commonly used to protect core laminations duringannealing is aluminum oxide although oxides of magnesium, Calcium,barium and the like have been used for this purpose. Other materialssuch as diatomaceous earths have also been used. In general, thesecoating materials are chemically inert and extremely fine, for example,of the order of 400 mesh, or finer, so that they are free-flowing.

To supply such coating material to the region in which the stack I 4 isbeing vibrated, there may be provided a hopper 40 terminating in adischarge pipe or spout 4| having at its lower end a valve 42 providedwith a handle or lever 43 actuable by the operator who during thevibration of the Stack may move the end of the spout 4| back and forthto distribute the coating material along the upper face of the stack.

During vibration of the Stack, the individual laminations rock abouttheir lower edges, Figs. 3a and 3b, and consequently when there is pro-Vided the proper relations between the inertia of thestack and thebiasing force applied by plate .66, the upper edges of the individuallaminations repeatedly and rapidly separate to allow progressive,intermittent flow between them of the coating material 44 piled on thetop of the stack. Preferably, during vibration of the Stack, theoperator' runs a riffling tool 45A, such as a fiat flexible springmember, along the exposed side edge of the stack to facilitate the flowof coating material to the lower edges of the laminations; otherwise theinterposed coating material might tend to form a wedge between adjacentlamination faces instead of a sheet of substantially uniform thickness.Alternatively, and as shown in Fig. '7, this rifiing of the side orlower edges of the stack may be performed automatically, as by arotating, spiral brush 45B mounted adjacent the stack. With very thinlaminations, it may be desirable to use a skeleton holder which in partexposes the other side of the laminations and/or the bottom edges.

During vibration of the Stack, the Ocatlng material progressively flowsdown between the laminations' and the stack, accordingly, grows orlengthens as exemplified by Figs. 4 to 6. Even with inexperiencedoperators, there can readily be obtained a coating between theindividual laminations which is quite uniform in thickness thrughout thelength of the Stack. As indicative of the growth of a Stack because ofthe interposed coating material, a Stack which originally may be only,for example 31/2 or 6 inches long, may be as long as 101/2 inches withina very short time. The extent to which a Stack grows during the coatingstep depends, of course, upon the number of laminations in the Stack,the usual lamination thickness being of the order of from O GQG to 0.014inch.

The time required to obtain coating of many hundreds of laminations in astack is of the order of only half a minute, which is many times shorterthan the time required for handstaeking: the diiferential, of course,varies with the size and., number of laminations in the Stack, with theindividual operators, and is the greater, the smaller the size of thelaminations: on an average, the time is reduced by a faetor of about 10.

ll/Ioreover, with the apparatus described, the time required for coatingof a stack of a given number of pieces and a given size' is about thesame for different operators, whereas with handstacking, the time variedwidely for different operators and for the same operator with differentsize of laminations.

Use of the apparatus is not limited to the coating of core laminationswith aluminum oxide or other' protective material. It may, for example,be used to coat laminations with a powdered binding agent, such aspowdered thermoplastics, or thermosetting resins, B'akeliteyor the like.In such case, the Stack after coating is heated while compressed tofusing temperature of the binder' which, upon Cooling, permanently holdsthe laminations together to form the core assembly of a transformer,choke, or the like, avoiding need for rivets, clamping bolts or thelike. Reverting to discussion of the coating as preliminary toannealing: when the laminations have between them a coating of desiredthickness, the holder is removed from the carriage I, the operator byhand maintaining pressure against the end plate IS to mantain the stackformation of the laminations. A plurality of such holders with coatedstacks are disposed in an annealing tray 46, Fig. 8, which is thenfilled with more of the powdered material 44 completely to cover thestacks. A plurality of such loaded trays are then disposed in anannealing box 41, Fig. 9, which is preferably shut to form a gas-tightenclosure for the tra-ys. The box 47, or usually several of them, arethen disposed in an annealing furnace and raised to annealingtemperature preferably during flow through the box M of hydrogen orother gas which is de-oxidizing or inert. The inlet and outlet pipes48-48 at the opposite ends of the box are provided for fiow of such gas.

At the end of the annealing operation, the trays are removed and theprotective material, now caked or hardened, is removed. Preferably asshown in Fig. 10, the material 44 is recovered for future use bycollection in a receptacle 49 provided with a screen 50. The individualworkholders are then removed from tray 46 and the remaining materialblown off by an air blast. AS ,shown in Fig. 11, the operator whilegrasping the work-holder IB in one hand, lightly presses against theslidable end wall 16 to retain the laminations in stack formation, andwith the other hand directs a blast of air from the nozzle 52 .againstthe laminations. The air blast riffles the loose laminations and blowsout from between them the remainder of the powdered coating material.Preferably and as shown in Fig. 11, this operation is performed in aclosed chamber 5| provided with an exhaust duct 53 to prevent the finepowder from being inhaled by the operator. Air under suitable highpressure is supplied to the nozzle 52 through a pipe 55 having ashut-off valve 55.

Thus, throughout the entire sequence of operations from Figs. 1 to 11,the laminations are retained in one and the same work-holder and aretransferred from one stage of operation to the next as a unit, the rodsll, or their equivalent, cooperating with the fixed and slidable Wallsof the holder to retain the laminations in Stack formation and preventtheir dislodgment during handling. Use of the apparatus described is notlimited to coating of core laminations: it is suited for coating ofstiff sheets of metal or non-metals. It is not suited for coating ofsheets which are of such material, or are so thin compared to theirwidth, that they flex substantially during vibration.

In general, the apparatus is suited for sheets whose thickness is fromabout .095 inch to about .015 inch and whose stiffness factor, which isproportional to the moment of inertia of the cross sectional shape ofthe lamination and inversely proportional to the cube of the length ofthe lamination, is within the range of from about 0.5 l09 to about 1510-9. The relation of its stiffness factor to the dimensions of thelaminations may be expressed as:

where K=stiifness factor w=width of lamination cross section t=thicknessof lamination l=length of lamination The coating materials suited forapplication to stacked laminations by the method described are generallyfree-:Flowing dry powders of fineness suitable to pass through av screenof the order of 400 mesh or finer.

What is claimed is:

1. Apparatus for coating stiff, flat laininations comprising holderstructure for loosely retaining the laminations on their lower edges inStack formation, means for vibrating said holder structure in directionsubstantially normal to the plane of each of said laminations, and meansfor supplying coating material to the upper edges of the stackedlaminations while held in said Vibrated structure whereby said coatingmaterial fiows between and coats said stacked laminations as they rockabout their lower edges in said Vibrated structure.

2. Apparatus for coating stiff, flat laminations comprising a frame,means for vibrating said frame, a work-holder for loosely retaining thelaminations on their lower edges in Stack formation, means fordetachably attaching said workholder to said frame, and means forsupplying coating material to the upper edges of the stacked laminationswhereby said material flows between and coats said stacked laminationsas they rock about their lower edges in the vibrated workholder.

3. Apparatus for Supporting Stiff, flat laminations in a region suppliedwith coating material comprising a holder having a movable end wall,means for biasing said movable end wall against a Stack of laminationsresting on their lower edges in said holder to retain them in Stackformation, and means for vibrating said holder in directionlongitudinally of the Stack intermittently to overcome the biasing forceby the inertia of the laminations whereby said laminations rock abouttheir lower edges and repeateclly slightly separate at their upper edgesto receive said coating material for fiow between them.

4. Apparatus for supporting Stiff, flat laminations in a region suppliedwith coating material comprising' a holder having a slidable end wall,biasing means exerting pressure through said slidable end Wall upon aStack of laminations resting on their lower edges in said holder withtheir upper edges disposed to receive said coating material, means forvibrating said holder in direction longitudinally of the stack wherebythe inertia of the laminations intermittently overcomes said pressurefor rocking of said laminations about their lower edges, and means forcontrolling the amplitude and frequency of the vibration of said holderto suit said apparatus for :'f

stacks of different characteristics weight and size.

5. Apparatus for coating laminations comprsing a holder for laminationsresting on their lower edges in stack formation, a Slidable end wallwithin said holder for engaging an end of the Stack, means comprisingrod structure attached to said slidable end wall and overlying thestacked laminations to confine them in Said holder, said rod structurein part projecting exteriorly of said holder, a biasing` weightconnected to the projecting part of said rod structure, means forvibrating said holder rapidly to rock the laminations about their loweredges, the inertia of the including vibrated laminations intermittentlyovercoming the biasing force of said weight whereby the upper edges ofsaid laminations repeatedly Slightly Separate, and means including adischarge pipe above said holder for supplying coating material to theupper edges of the stacked laminations for flow between them duringvibration of said holder.

6. Apparatus for Supporting magnetic core laminations in a regionsupplied with powder of nature protecting them during annealingcomprising holder structure for loosely retaining therein a stack ofsaid laminations resting on their lower edges, biasing means forapplying to the Stack a compressive force retaining the laminations inStack formation 'With their upper edges positioned to receive saidpowder, a frame to which said holder structure is detachably held, andmeans for vibrating' said frame in direction longitudinally of the Stackwhereby the inertia of the laminations intermittently overcomes saidcompressive force, said laminations rocking about their lower edges andrepeatedly slightly separating at their upper edges to receive saidprotective powder for fiow between them.

CARL J. CROSS. SHERMAN W. LYNCH.

.REFEREN CES CITED The following references are of record in the f'le ofthis patent:

UNITED STATES PATENTS Number Name Date 805,095 Ridd Nov. 21, 19051,354,061 Palmer Sept. 28, 1920 l,482,607 Gow Feb. 5, 1924 1,666,044Danziger Apr. 10, 1928 1,782,536 Kirschbraun Nov. 25, 1930 1,838,701Nicolai Dec. 29, 1931 2,163,642 Wallach June 27, 1939 2,187,617 FoggJan. 16, 1940 22471794 Wallach July 1, 1941 2,412,954 Zdancewicz Dec.24, 1946

